Right Now: TCAP Review Get new 7.2 notes

Agenda: 1. Notes: 7.2 part I 2. Complete Air Masses map 3. Describe Air Masses in graphic organizer

TN Standard: Analyze meteorological data to predict weather conditions

February 10, 2015

AIR MASSES

Today we’ll learn about air masses and their effect on weather.

THINK ABOUT IT…

Write down as many different qualities of air as possible…

An AIR MASS is a large body of air where temperature and moisture contentare similar throughout.

Changes in weather are caused by themovement and interaction of air masses.

Air Masses characterized by:• moisture content• temperature

The moisture content and temperatureare determined by the AREAover which the air mass forms.

These areas are called source regions.

There are many types of air masses, eachassociated with a particular source region.

The characteristics of these air masses arerepresented on maps by a two-letter symbol.

The first letter indicates the moisture content characteristic of the air mass.

The second letter represents the temperature that is characteristic of the air mass.

mT

MOISTURE CONTENT

maritime (m) forms over water Wet

continental (c) forms over land dry

Types of Air Masses

TEMPERATURE

polar (P) forms over the polar regions cold

tropical (T) develops over tropics warm

Cold Air MassesMost cold winter weather in the U.S. is influenced by three polar air masses.

1. (cP) continental polar – forms over northern Canada -brings extremely cold winter weather to the U.S. In summer, a cP air mass brings cool, dry weather.

2. (mP) maritime polar – forms over the North Pacific Oceanis cool and very wet. Brings rain and snow to Pacific Coast in winter and cool, foggy weather in summer.

3. (mP) maritime polar air mass that forms over the North Atlantic Ocean brings cool, cloudy weather and precipitation to New England in winter. In summer, it brings cool weather and fog.

Four warm air masses influence weather in the U.S.

4. (mT) Maritime tropical that develops over warm areasin Pacific Ocean is milder than maritime polar air massthat forms over Pacific Ocean. Same weather as #6 mT.

5. (mT) Maritime tropical air mass develops over the warm waters of the Gulf of Mexico and towards the Midwest.

6. (mT) Maritime tropical forms over the warm Atlantic Ocean,and moves north across the East Coast.BOTH: In summer, they bring hot and humid weather, hurricanes,and thunderstorms. In winter, mild and cloudy weather.

7. (cT) Continental tropical air mass forms over deserts of northern Mexico and southwest U.S. It moves northwardand brings dry, and hot weather in summer.

Is humid air heavier than dry air?

What do you think?

People often assume humid air is heavierthan dry air.

Humid air rises like a balloon because itis less dense than dry air at same pressure and temperature.

Water molecules are lighter than nitrogenand oxygen which makeup air.

The more water vapor in a mass of air,the more nitrogen and oxygen is displaced.

When humidity increases, air becomes lessdense and rises.

As an air mass rises, it cools.

The water vapor condenses, and air masseventually sinks.

If water vapor were heavier than air,clouds would form only at the Earth’s surface.

Using your map of North America – Draw RED or BLUE colored arrows (according to temperature) andindicate the source regions of North American air masses.

LABEL each air mass by its two-letter symbol. (4 warm and 3 cold air masses as shown on page 192).

IN CLASS

mT

Look at page 192 in textbook

How do you think air masses that form over the land and oceanaffect weather in the United States?

*Putting it together…

Use your graphic organizer and textbookpage 193 to classify:

• 3 COLD AIR MASSES• 4 WARM AIR MASSES

END OF AIR MASSES PPT

Meteorological data suggests that a warm frontis coming.

What sort of weathermight be predicted?

PUTTING IT TOGETHER…

Drizzly rainfollowed by clear, warm

weather!